There are various different possibilities of heating and humidifying breathing air. The goal is to supply the patient with humid and preheated air. The problem in breathing gas humidification is to adjust the humidity supplied to the velocity of flow and to the gas flow. This adjustment is necessary to avoid overheating of the breathing gas, on the one hand, and to extensively prevent the formation of water of condensation, on the other hand. Breathing gas humidifiers in which water is heated in a water reservoir and is fed into the flowing breathing gas in the form of water vapor are known.
Water traps or also desiccants, which collect the water of condensation passively at the device, are used for dehumidification and for removing water of condensation. However, it cannot be avoided that the formation of water of condensation will nevertheless take place within the respiration system. Heating foils, with which the respiration system can be heated over a large surface, are known for reducing the formation of water of condensation within the respiration system. The problem is additionally aggravated in the case of a closed breathing circuit in anesthesia by the fact that moisture, which must be removed from the system, is formed additionally due to the absorption of carbon dioxide in the carbon dioxide adsorber. Filter systems, which initially heat the inspired gas in the form of a heat exchanger and extract moisture from the expired gas, are known for reducing the moisture in the breathing gas. The moisture of the breathing gas, which moisture is being stored in the filter, is again introduced into the inspired gas during the next inspiration stroke. Such a filter is known from EP 533 644 A2. The drawback of the prior-art filter is that only a limited quantity of moisture can be stored.